Posology : מינונים

4.2   Posology and method of administration

The dosage of Fentanyl should be individualized according to age, body weight, physical status, underlying pathological condition, use of other drugs, and type of surgery and anesthesia.
To avoid bradycardia, it is recommended to administer a small intravenous dose of an anti-cholinergic just before anesthetic induction.
- Use as an analgesic supplement to general anesthesia
Low dose: 2 μg/kg
Fentanyl in small doses is most useful for minor surgery.
Moderate dose: 2-20 μg/kg
Where surgery becomes more complicated, a larger dose will be required.
The duration of activity is dependent on dosage.
High dose: 20-50 μg/kg
During major surgical procedures, in which surgery is longer, and during which the stress response would be detrimental to the well-being of the patient, doses of       20-50 μg/kg of Fentanyl with nitrous oxide/oxygen have been shown to have an attenuating effect. When doses in this range have been used during surgery, post-operative ventilation and observation are essential in view of the possibility of extended post-operative respiratory depression.
Supplemental doses of 25-250 μg (0.5-5 ml) should be tailored to the needs of the patient and to the anticipated time until completion of the operation.
- Use as an anesthetic agent
When attenuation of the response to surgical stress is especially important, doses of 50-100 μg/kg may be administered with oxygen and a muscle relaxant. This technique provides anesthesia without necessitating the use of additional anesthetic agents. In certain cases, doses up to 150 μg/kg may be required to produce this anesthetic effect. Fentanyl has been used in this fashion for open heart surgery and certain other major surgical procedures in patients for whom protection of the myocardium from excess oxygen demand is particularly indicated.
- Epidural Administration for Postoperative Management of Pain
100 mcg may be administered epidurally. The 2 ml ampoule should be diluted with 8 ml of 0.9% Sodium Chloride Injection, resulting in a final concentration of 10 mcg/ml. The quality and duration of epidural analgesia with fentanyl appears to be concentration-dependent below serum levels of 10 mcg/ml with no significant improvement obtained by increasing concentrations above this value. Additional boluses may be administered if there is evidence of lightening of analgesia.
For immediate use after dilution.
Special populations
- Elderly and debilitated patients
As with other opioids, the initial dose should be reduced in elderly (>65 years of age) and in debilitated patients. The effect of the initial dose should be taken into account in determining supplemental doses.
- Pediatrics
For induction and maintenance in children aged 2-12 years, a dose of 2-3 μg/kg is recommended.
Obese Patients
In obese patients there is a risk of overdosing if the dose is calculated based on body weight. Obese patients should be dosed based on estimated lean body mass rather than on body weight only.
Renal Impairment
In patients with renal impairment reduced dosing of should be considered and these patients should be observed carefully for signs of fentanyl toxicity (see Pharmacokinetic properties).